Fish Counter Development
Logie 2100 Resistivity Counter
The Logie 2100C (Aquantic Ltd., Scotland) is a resistivity counter, which detects the passage of fish across an array of three electrodes. The counter electronics continually monitor the resistance of the water above the counting array (bulk resistance) and calibrates for changes in this resistance every 30 minutes. When a fish passes through the electrode array, a change in resistance occurs, as a fish is more conductive than the water it displaces. This change of resistance is recorded and analyzed by the counter using a firmware algorithm to determine if it fits a typical fish pattern. Should the counter assess that a fish has passed over the array (based on this comparison), the time, direction of travel and peak signal size (change of resistance measurement) of the fish event, is recorded and stored for later downloading and analysis (see Aprahamian et. al. (1996) for more details of counter design and operation).
Where are Logie 2100 Resistivity Counters used?
Quantitative stock assessment of adult migratory salmonids in freshwater has been a key management tool for stock monitoring and management. A variety of methods have been used to enumerate salmonids these include the use of mechanical, resistivity, and acoustic counters, video and optical counters, mark recapture, hydroacoustic methods, catch data and full river traps. The choice of method is dependent on the need for accuracy for management purposes as well as the cost of obtaining the data.
Resistivity counters have shown the ability to accurately enumerate fish stocks with minimal maintenance, for example coho and pink salmon or steelhead trout, McCubbing and Ward (1998) or Atlantic salmon and sea trout, Aprahamian et. al. (1996)
Sites in North America where Logie 2100 counters are currently in operation:
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